On Sun, Jun 14, 2020 at 7:56 AM Frank Zingsheim <f.zingsheim@gmx.de> wrote:
Thank you for your comments.
[...] 
(2) You say "initial value" several times when you mean "final value".
The reason why I called it initial is the recursion which is build up to generated the code for ( C ? E : ... : I )

(I)
(C(N) ? E(N) : (I))
(C(N-1) ? E(N-1) : (C(N) ? E(N) : (I)))
(C(N-2) ? E(N-2) : (C(N-1) ? E(N-1) : (C(N) ? E(N) : (I))))
...

What I notice about each of those expressions is that (I) appears last in each of them. Hence, it's the "final" subexpression in every single one.
"Initial" means "first/leftmost"; "final" means "last/rightmost."

Furthermore, in the first proposal P1012R0 https://github.com/zingsheim/ProposalTernaryFold/blob/P1012R0/ProposalTernaryFold.md there was a comparison to binary fold expressions and in a fold like (values + ... + 0) you would call the 0 the initial value and not the final value.

I certainly would not!
I don't see any precedent-making use of the term "initial value" in http://eel.is/c++draft/expr#prim.fold either, although I just glanced briefly at it.

However, since the conditional operator is the only ternary operator in C++ the wording "final expression" might be more suitable or even "default expression", since it is comparable to the "default:" of a "switch" statement. What do you think?

I think "default [sub]expression" or "default value" would also be reasonable.

To you comments to the + on the string_view you are right (what should the + return, definitely not a string_view).
But do you know why std::string + std::string_view does not work and one has to use std::string.append instead?

I don't know for sure, but I suspect that it has to do with overload resolution. If you permit string + string_view, then you also permit string + (anything implicitly convertible to string_view), which means that if someone has a QString that is convertible to both string and string_view, then suddenly (string + QString) becomes ambiguous.
Implicit conversions are the devil.
 
[...]
For the hyperlinks I tried to add them. They work on Typora (a markdown editor) but unfortunately they do not work on Github (https://github.com/zingsheim/ProposalTernaryFold/blob/progress/ProposalTernaryFold.md). Do you know what might be wrong with their formating?

Right now you have this:
It can be emulated by the fold on operator|| [[5]](######[5] foonathan::blog(): Nifty Fold Expression Tricks: Get the nth element (where n is a runtime value) https://foonathan.net/2020/05/fold-tricks/).
You should have this instead:
It can be emulated by the fold on operator|| [[5]](#5-foonathanblog-nifty-fold-expression-tricks-get-the-nth-element-where-n-is-a-runtime-value-httpsfoonathannet202005fold-tricks).
I got the name of that HTML anchor by clicking on the "chain link" icon that appears to the left of note 5 when you mouse over it, and then cutting and pasting from the browser address bar.

–Arthur